Applications Of Nucleic Acid Nanomaterials And Dendrimers In Gene Diagnosis And Therapy Of Cancers

Cancer is a serious threat to human life and health.Basic research and translational medicine research related to cancer have become the focus of extensive attention worldwide.Gene detection method using cancer-related point mutations as biomarkers can achieve early diagnosis of tumors,but it faces the dilemma of low abundance of point mutations,low detection sensitivity and complicated design.Adenovirus-based gene therapy plays a role in the field of cancer therapy,which can reduce a series of side effects caused by physical and chemical therapy.However,adenovirus is easy to be cleared in the blood and has no targeting ability.Therefore,the development of new technologies to provide new ideas to solve the problems in cancer gene detection and gene therapy will be conducive to improving the effect of cancer diagnosis and therapy.In this thesis,the applications of nucleic acid nanomaterials and polyphenylene dendrimers in cancer-related gene diagnosis and gene therapy are studied.In the field of cancer-related gene diagnosis,DNA nanorobot and DNA wedge element were constructed to optimize the functions of diagnostic methods for the enrichment and detection of the point mutation,respectively.In the field of gene therapy,the polyphenylene dendrimers and dendrons were used to construct modification platforms to enhance the infecting,shielding and targeting ability of adenovirus.The thesis mainly includes the following contents:(1)A nanorobot capable of specifically recognizing wild-type DNA was constructed by DNA origami.The interfering wild-type DNA was removed in the pretreatment stage,so that the abundance of mutant DNA was increased.Nanorobots are composed entirely of DNA,minimizing the problem of non-specific adsorption of target DNA and achieving a detection limit of at least 0.1%.Compared with other enrichment methods,this method has the advantages of simple process,short duration,and resettability.(2)A novel regulatory element of strand displacement reaction,DNA wedge,was designed and constructed.It can achieve a bidirectional and fine regulation of the strand displacement reaction.The wedge element has simplicity,versatility and compatibility,and have great application potential in the construction of DNA nanodevices.At the same time,the addition of wedge elements could simplify the optimization process of the strand displacement reaction system.Based on this,we designed a “signal-inhibited” detection probe for gene mutation,which has a detection limit of at least 1% and a detection time as low as 30 minutes,and can detect unknown mutations.(3)The rigid spherical polyphenylene dendrimer PPD3 with amphiphilic n-propyl and sulfonic acid surface patches was designed and synthesized to simulate the surface patterns of proteins.PPD3 bound to the surface of adenovirus formed a synthetic polymer corona that greatly altered various host interactions of adenovirus as well as in vivo distribution.The dendrimer corona significantly improved the ability of adenovirus to transduce cells deficient for the primary adenovirus cell membrane receptor and modulated the binding of adenovirus to blood coagulation factor X.It also protects adenovirus from neutralization by natural antibodies and the complement system in human whole blood.(4)The dendrons were taken as the binding molecule of adenovirus,and were assembled with other functional modules through a click reaction or a biotin-streptavidin connecting system.The dendrons form a functionalized “polymer corona” on the surface of the adenovirus,which offer a platform for introducing bioactive groups on the surface of the adenovirus.On this basis,the feasibility of adenovirus targeted infection of tumor cells was verified.This provides a foundation for the realization of targeted gene therapy.Through the above researches,this thesis can provide a new reference for solving the problems in the field of cancer-related gene mutation enrichment and detection,and remedying the defects in the application of adenovirus to cancer gene therapy.It may better serve the development of clinical application with new technologies and new methods.